Electronic tube circuit



NV- 28, 19.44 o. H. SCHADE' ELECTRONIC TUBE' CIRCUIT 'Filed Jan. 20,1943 l ....DaPDO mmJDa E m w Vl m55 Dn mH yo wm .m mr 0 Vl B PatentedNov. 28, 1944 ELECTRONIC TUBE CIRCUIT" om n. schade, West Caldwell, N.J., assigner to Radio Corporation oi America, a corporation of DelawareApplication January 20, 1943, Serial No. 472,952

6 Claims.

This invention relates to an improvement in impulse mixer circuits, andmore specifically to an improvement in `a circuit arrangement for mixingimpulses in a television system where the impulses correspond to thehorizontal and ver-` tical deection frequencies.

In the transmission of television signals, as is ywell known to thoseskilled in the art, some means must be providedfor maintainingsynchronous operation of the various receivers with the transmitter.This is accomplished by transmitting a series of synchronizing impulseswhich, when received at the television receiving apparatus, areeffective to maintain the desired degree of synchronism. In order thatthe' necessary degree of synchronism may be maintained, it is desirablevto transmit a synchronizing impulse corresponding to each line scanned,and a further synchronizing impulse corresponding to each field scanned.The line scanning rate and/or the eld scanning rate `may be altered tosuit particular circumstances, but in any event, synchronizing impulsesof relatively short duration are generally transmitted corresponding toeach of these parameters.

In the .conventional transmission of television signals, the linesynchronizing impulses are transmitted during the interval betweenpicture signals representative of each line, and the field synchronizingimpulses are transmitted during the interval between picture signalsrepresenta# tive of each field. In an electronic television system,these synchronizing signals initiate the horizontal andvertical returnof the cathode ray beam.

In television transmitting systems, impulses of both line and eldfrequencies are also used to blank or obliterate picture signals whichmay be produced during the return deflection of the scanning cathode raybeam or, as an alternative, impulses of line and eld frequencies ,may beused to interrupt the scanning cathode ray beam orv For e (Cl. TIS-69.5)

In most television transmitting systems, an impulse generating system isprovided which produces impulses ofline and eld frequency in order thata denite relationship may be maintained between the frequencies of thetwo series of impulses, and through the use of frequency dividercircuits, the line and field series of impulses may be derived fromdierent parts of the impulse generating system. When these impulses areapplied to an impulse mixing or combining circuit, they are combined sothat the produced series of impulses will represent e a composite ofboth the line and field impulse series.

Various mixer circuits have heretofore been used, but frequently suchcircuits are not of optimum desirability in that they do not produce thedesired wave form in a composite impulse series, or they may require anexcessive inputy voltage to produce the desired final wave form.Furthermore; presently known impulse mixing circuits are somewhatcomplex and include a great number of tube elements and parts. In thepresent invention, an impulse mixing circuit has been provided which issimple in operation and which will produce a desired composite wave formby the application of a relatively low intensity controlling impulseseries.

One purpose of the present invention, therefore, resides in theprovision of an impulse mixing circuit which is simple in operation, andwhich embodies the use of a limited. number of tube and circuitelements.

Another purpose of the present invention resides 'in the provision of animpulse mixing circuit wherein it is possible to produce a desiredcomposite wave form, the impulse mixing circuit being initiated byrelatively low intensity impulses of line and eld frequency.

A still further purpose of the present invention resides in theprovision of an impulse mixer circuit in which tilted or peaked impulsesmaybe applied to the mixer circuit without affecting the wave form ofthe composite series of impulses.

Still other `purposes and advantages of the present invention willbecome more apparent to those skiued in the art from the foiiowingdepling condenser 40.

streams or paths may be enclosed within the same tube envelope or, aswill be appreciated, two

separate tube envelopes may be used..

One of the electron streams or paths a cathode I2, a control electrodeI4 and an an'ode includes I6. The other electron path includes a cathodeshown) by way of anode resistance 26.-.- AThe 1 control electrode I4 ismaintained at apotential slightly positive with respect to the cathodei2 by means of a potential divider including resistances 2B and 30 whichare connected in series between the positive terminal 24 and thenegative terminal or ground. The control electrode I4. is connected tothe junction of these resistances, and the potential of the controlelectrode I4 with respect to the cathode l2 may be determined byproperly proportioning the value of the resistances.

The cathode I8 of the second electron path is connected to ground by wayof cathode resistance 32, while the anode 22 is connected to thepositive terminal 24 by means of the anode load resistance 34. Apotential divider including series resistances 36 and 38 is connectedbetween the positive .terminal 24 and the negative terminal or ground,while the control electrode is connected to the junction of theseresistances. The potential of the control electrode 20 relative toground may, therefore, be controlled by proportioning thek resistances36 and 38. The anode I6 of the first electron path is connected to thecathode I8 of the second electron path by means of a cou- Impulses ofhorizontal or line deflection frequency are applied to the inputterminals 42 and 44', these terminals beingA connected respectively tothe control electrode I4 of the rst electron path and to ground. The`horizontal impulses may have a Wave form such as indicated at 46, the'frequency of the impulses corresponding to I the line deflectionfrequency. When impulses of such a wave form are applied to the controlelectrode I4, a potential variation is available at the anode I6 similarto the wave form shown at 48. The bias of the control electrode I4relative to the cathode I2Iis such that the first electron path performsa clipping action on the applied impulses with the result that theimpulse peak is removed. Naturally, the polarity of the impulses isreversed due to the phase inversion operation of the tube. Theseimpulses, as represented at 4B, are then applied to the cathode I8 ofthe second electron path tomodulate the cathode potential relative toground.

Impulses .of vertical or eld deflection frequency-are' applied to theterminals 50 and 52 preclude the passage of current to anode 22.

The impulses of line deflection frequency as represented at 48 which areapplied to the cathode I6 are also `oi? sufficient intensity to causethe tube 'to be vblocked by driving the cathode I8 positive.

Current through the second electron path. is. therefore, interruptedboth during the applica'- tion of impulses of line frequency to thecathode I8, and during the application-of'eld impulses to the controlelectrode 20. Modulation of the electron stream in the second electronpath, therefore, varies the amount of current in the anode circuit withthe result that a potential variation may be derivedfrom the anode 22which is representative of the combined series of impulses. Thispotential variation may be derived from output terminals .56,and 58, theformer being connected to the anode 22 by way of a relatively largecondenser 60, -while the terminal 58 is connected to ground or somepoint of xed potential. The output terminals 56 and 58 are connectedtogether by a variable resistance 62 of a relatively low value.

In order that the second electron path including cathode I8 and anode 22may be driven to cut-off by cathode modulation, the anode resistance 34is made relatively large in order to reduce the plate voltage at theanode 22 in orden that the impulses of line frequency as applied to thecathode I8 may produce a sharp cut-off of the 'for example, by thedotted line 55 associated with the Wave form curve 54. The composite ormixed impulses which are available from the anode 22 of the secondelectron stream are, therefore, positive inv polarity and arelpreferably derived by Way of a relatively low alternating current loadin order to maintain goud wave form. The low impedance alternatingcurrent loadv is produced by means of the relatively large condenser 60.andv the relatively small resistance 62.

In order that proper direct current potentials may be applied to thecontrol electrodes I4 and 20, the resistance 30 is generally chosen toequal approximately 10% of the value of resistance 28, while theresistance 38 is generally chosen to equal approximately 5% of theresistance 36. The cathode resistance 32 may have a value ofapproximately 500 to 1,000 ohms While the anode resistance 26 for thefirst electron path may have a value from 15,000 to 50,000 ohms. Asexplained above, in order to produce a sharp cut-olf in the secondelectron path, the anoderesistance 34 should preferably have a fairlyhigh value corre- Y sponding to approximately 200,000 ohms.

For performing the combining or mixing operation, the tube I0 may be ofthe type 6SM-GT or type 7F?, although it is to be understood thatvarious other single or dualpurpose tubes may be used wheredesired.

The base line of the mixed impulses, as represented by the wave form 64and available from the output terminals 56-58', can be made perfectly ator it maybe tilted to a desired degree for one or both of the input'impulse series by pre-tilting the base line of the Wave forms suppliedto either of the control electrodes le or 20.

46 that the horizontal vimpulses as applied to the input terminals 42and44 extend in a negative direction. lf, however, vthe available impulsesof horizontal deflection frequency should extend in a positivedirection, a similar mixing circuit could be used by providing cathodecoupling between the two triode sections of the tubeV l0. I1' horizontalimpulses of such polarity are applied to the input terminal 42, it wouldstill be desirable to apply positive impulses of horizontal deflectionfrequencyto the cathode I8 of the triode section including cathode I8,control electrode 20 andanode 22. In this case, the coupling condenser40 would be omitted and the cathode l2 would be directly connected tothe cathode I8 in 'order to aiord the desired cathode coupling. Thecathode resistance 32 would then be common to both cathode electrodes.

With such a slight revision it would then be possible to applyhorizontal impulses having a pclarity reversed with respect to thoseshown in the gure, and still utilize the present invention for affordinga circuit arrangement for mixing the horizontal and vertical impulses.The samel tube types as suggested above could be used, or, if

desirable, a tube such as the type 6SC7 could be 4,

employed since this particular tube type has a common cathode electrode.

Furthermore, it is conceivable that the application of the horizontaland vertical impulses to the cathode I8 and control electrode`2ll couldbe reversed, assuming, of course, that the polarity of the impulses issimultaneously reversed. Under these conditions, vertical impulses thatextend in a positive direction could be applied to the cathode I B, andhorizontal impulses extending in a negative direction could be appliedto the control electrode 20. These latter impulses would be derived fromanode I6 by Way of condenser 40 and would result from the application ofhorlzontal impulses to the control electrode I4, the pulses extending ina positive direction. It is desirable that the polarity of the appliedpulses operate to 'bias the control electrode- 20 with respect to thecathode I8 such that electron flow to the anode 22 is precluded.

In the present invention, the duration of the individual horizontalimpulses corresponds tol about 7% to 8% of the horizontal deectionnterval, and the duration of the vertical impulses corresponds to about1.0 or 1.5 horizontal deflection cycles. It is to be understood,however, that impulses of different time duration could as Well be usedin the present invention.

Through the use of the present invention it may, therefore, be seen thatan effective and efficient impulse mixing or combiningcircuit has beenprovided which will respond to applied impulses of relatively lowintensity, and which will produce theV desired composite wave form eventhough some tilting or peaking may be present in the applied impulses.Furthermore, it will be appreciated that all of the impulses of thecomposite series as represented by the curve 64 have the same intensity,their duration and frequency being determined by the duration andfrequency of the applied horizontal and vertical impulse series. Itwill'lalso be appreciated that an irnpulse mixer circuit has beenprovided which will produce a composite series of impulses without inany Way affecting the operation or action of the sources from which theindependent series of horizontal and vertical impulses are derived.

Although the present invention has been described somewhat in detail, itwill be appreciated that various alterations and modifications mayv bemade therein without departing from the spirit and scope thereof, and itis desired that any and all such alterations and modiflcations beconsidered Within the purview of this invention except as limited Ibythe hereinafter appended claims.

Havingnow described my invention, what I claim as new and desire to haveprotected by Letters Patent is: Y

l.4 An impulse mixer for combining two series of impulses, the impulsesof each series differing in time duration and frequency, comprising arst and second electron discharge path each including a cathode. acontrol electrode, and an anode, an

anode load .impedanc-e associated with each electron discharge path,means for 4applying the lmpulses of one of the series to the'controlelectrode of the rst electron discharge path to produce vvoltagevariations of corresponding time duration and frequency across the loadimpedance of that path, means including a coupling condenser forapplying the voltage variations produced across the load impedance ofthe first electron discharge path to the cathode of the second electrondischarge path, means for ,applying the other series of impulses to thecontrol electrode of the second electron discharge path whereby theimpedance of the second electron discharge path will be altered by boththe applied produced voltage varia- I tions and the other applied seriesof impulses.

` the series tothe control electrode of the rst elecand an outputcircuit coupled-across the anode load impedance of the second electrondischargepath.

2. An impulse mixer circuit for combining two series of impulsescomprising a rst and second` electron' discharge path each including acathode, a control electrode and an anode, an anode load impedanceassociated with each electron discharge path, means for applying theimpulses of one of the series to the control electrode of the firstelectron discharge path to thereby produce corresponding voltagevariations at the anode of that path, means for applying the voltagevariations produced at the anode of the rst electron discharge path andthe other series ofimpulses to the cathode and control electrodefof thesecond electron discharge path' to produce a series of voltagevariations corresponding to the combined series of impulses, and anoutput circuit associated with the second electron discharge path. y

3. An impulse mixer circuit f or combining two series of impulses, theimpulses of each series differing in time duration and frequency,comprising a first and second electron discharge path each including `acathode, a control electrode and an anode, means to apply the impulsesof one of tron discharge path to thereby produce voltage variations ofcorresponding time duration and frequency across an anode load circuitassociated with the path, and means to apply the voltage variationsproduced across the anode load circuit and the other series of impulsesto the cathode one frequency to the control electrode of the first Lelectron current path to produce voltage variations of a correspondingfrequency at the anode of that electron current path, means for applyingthe voltage variations produced at the anode of the first electrondischarge path to the cathode of the second electron current path, meansfor applying the impulses of said another frequency to the controlelectrode of the second electron current path, the applie'dproducedvolt- 5. An impulse mixer circuit for combining a series of impulses ofone' frequency with arseries y of impulses of another frequencycomprising a first and second electron dischargepath each having acathode, a control electrode and an output electrode, means for applyingthe impulses of the one frequency to the control electrodeof the firstelectron discharge path to produce corresponding potential variations atthe output lelectrode of that electron discharge path, means forapplying the potential variations produced at the output electrode ofthe first electon'discharge path to the cathode of the second electrondischarge path, and means for applying the voltf age variations of theother frequency to the con- 'trol electrode of the second electrondischarge path, the applied produced potential variations and theapplied impulses of the other frequency being effective to modulate theelectron stream in the second electron discharge path to produce voltagevariations representative of the combined impulses of both frequenciesat the output electrode of the second electron discharge path.

6. An impulse mixer circuit for use in a television system for combininga series of impulses of line frequency with a series of impulses ofiield frequency comprising a first and second electron discharge patheach including a cathode; a control electrode and an anode, means toapply impulses of line frequency to the control electrode of the rstelectron discharge path to produce corresponding voltage variations atthe anode of that electron discharge path, means to apply the voltagevariations produced at the anode of the first electron discharge path tothe cathode of the second electron discharge path, means to apply theimpulses of eld frequency to the control' representative of both lineand field frequency at the anode of the second electron discharge,

path, and an output terminal connected to the anode of said secondelectron discharge path OITO H. SCHADE.

